The present invention relates to an optical bioinstrumentation device for noninvasively measuring the concentrations of components in the living body by means of light, a measurement site holder in which the measurement site is placed, and a method of manufacturing the same.
For example, devices which perform spectroscopic measurements and devices which perform magnetic measurements are known as devices for acquiring information concerning the living body of a patient being examined in a noninvasive manner (noninvasive meaning that there is no need to insert a device or instrument through the skin or bodily orifices for the purpose of diagnosis or treatment). The devices described in Japanese Patent Application Laid-Open No. S60-236631 and U.S. Pat. No. 5,237,178 perform quantitative measurements of components in the living body in noninvasive manner by spectroscopic means.
The devices described in these patents are devices that measure the glucose concentration (blood sugar level) in the living body of the patient being examined in a noninvasive manner. In the device described in Japanese Patent Application Laid-Open No. S60-236631, a construction in which the ear lobe (measurement site) of the patient being examined is illuminated from the outside with light, and the transmitted light that passes through the ear lobe is detected by a photo-detector attached to the inside of the ear lobe by means of adhesive tape, a strap or the like, and a construction in which a photo-detector is applied to the surface of the patient""s body (measurement site), and scattered and reflected light are detected, are disclosed.
In the device described in U.S. Pat. No. 5,237,178, a construction is disclosed in which a finger tip stopper and a sponge rubber used to hold the finger are used as finger insertion means for positioning the finger, and the transmitted light that is transmitted through the finger (measurement site) is detected by a photo-detector.
Furthermore, in conventional noninvasive measuring devices, living-body information for a plurality of patients is acquired separately, and the living-body information thus acquired for individual patients is recorded on a recording medium which is installed inside or outside the abovementioned measuring device. The living-body information for individual patients that is recorded on this recording medium is read out on subsequent occasions when living-body information is to be acquired by these patients, and (for example) when diagnoses are made by physicians or when judgements are made by the patients themselves.
However, in the case of such prior art, the measurement conditions fluctuate according to the positional relationship between the measurement site and the photo-detector, so that the problem of measurement error arises.
Specifically, since the distribution of components in the living body is not uniform, the light path at the measurement site shifts (for example) if there is any shift in the mounting position of the photo-detector with respect to the measurement site, or any shift in the set position of the measurement site with respect to the device in which the photo-detector is mounted, so that the information contained in the light that is emitted from the living body fluctuates, thus resulting in the occurrence of measurement error. Furthermore, in cases where measurements are performed with the photo-detector pressed against the measurement site, there is a variation in the manner of flow of subcutaneous blood as a result of fine differences in the pressing force, in addition to a variation in the light path length accompanying shape deformation of the measurement site; as a result, the variation in measurements is increased, so that measurement error occurs.
Furthermore, since living-body information for numerous patients is recorded on the recording medium installed in a conventional measuring device, living-body information for individual patients may be erroneously acquired. In cases where living-body information for individual patients is thus erroneously acquired, this may lead to (for example) erroneous diagnoses by physicians or erroneous judgements by the patients themselves.
When living-body information is acquired by patients on subsequent occasions, and (for example) when diagnoses are made by physicians or when judgements are made by the patients themselves, the living-body information that is recorded on the recording medium installed in the measuring device must be read out. Accordingly, the same measuring device must be used, so that the convenience to the patients is poor.
It would appear that these problems are becoming more conspicuous as a result of the increasing commonness of living-body measurements for multiple numbers of patients in the household with the development of an increasingly aging society in recent years.
The present invention was devised in order to solve such problems. It is an object of the present invention to provide a noninvasive optical bioinstrumentation device which allows highly precise quantitative measurements of components in the living body. Furthermore, it is also an object of the present invention to provide a measurement site holder used in such an apparatus, which prevents erroneous diagnoses and erroneous judgements, and which offers increased convenience to the user.
The noninvasive living body optical measuring device of the present invention is a noninvasive optical bioinstrumentation device in which a specified measurement site in the living body is illuminated with light, the light that is transmitted through this measurement site or the light that is scattered and reflected by this measurement site is detected by a photo-detection system, and the concentrations of components in the living body are measured from this detected light, this device being wherein the device is equipped with a measurement site holder which is constructed using a negative impression of the measurement site, and in which the measurement site is placed at the time of light detection.
In a noninvasive optical bioinstrumentation device constructed as described above, the measurement site holder is constructed using a negative impression of the measurement site; accordingly, this measurement site holder can be caused to fit or conform to the shape of the patient""s measurement site. Accordingly, the measurement site can be positioned with good precision when the measurement site is placed in the measurement site holder at the time of light detection, so that shifts in the light path at the measurement site are reduced compared to those in a conventional device. Consequently, variations in the measured values caused by the non-uniform distribution of components in the living body are reduced, and variations in the shape of the measurement site are reduced compared to those seen in conventional devices, so that variations in the measured values caused by variations in the light path length accompanying changes in the shape of the measurement site, or by variations in blood flow due to differences in the contact pressure or the like, can be reduced.
Here, if the measurement site holder has a detachable structure, then the same device can be used in common by numerous patients, by selecting a measurement site holder that fits or conforms to the shape of the patient""s measurement site, and mounting this measurement site holder on the device.
Furthermore, if the measurement site holder is manufactured as a negative impression of the measurement site for each individual patient, then this measurement site holder will conform to the shape of the measurement site, so that variation in the measured values can be minimized.
Furthermore, if the measurement site holder is equipped with an opening part that allows the illumination of the measurement site with light, and an opening part that makes it possible to guide the transmitted light or scattered and reflected light from the measurement site into the photo-detection system, or if the measurement site holder is equipped with a single opening part that allows the illumination of the measurement site with light and that makes it possible to guide the scattered and reflected light from the measurement site into the photo-detection system, then the position at which light is incident on the measurement site and the position at which light is emitted from the measurement site can be accurately fixed, so that variation in the measured values is further greatly reduced.
Furthermore, if the inside contact surface of the measurement site holder that contacts the measurement site is coated with a coating material that absorbs light in the measurement wavelength region, then fine variations in the light path length in the living body caused by the reflection of light at the contact surface between the measurement site holder and the measurement site can be prevented, so that variation in the measured values is further greatly reduced.
Furthermore, it is desirable that the photo-detection system be equipped with a birefringent interferometer which converts the transmitted light or scattered and reflected light into split light by using a polarized light splitting birefringent element to split the light into polarized light with mutually perpendicular vibrational planes, and which causes this split light to converge so that an interferogram that makes it possible to measure the concentrations of components in the living body is obtained.
As a result, since an interferogram based on the light that is transmitted through the measurement site of the living body or the light that is scattered and reflected by this measurement site is obtained via a polarized light splitting birefringent element, the concentrations of components in the living body can be measured. Such a birefringent interferometer equipped with a polarized light splitting birefringent element has a simple construction without any mechanical driving parts; accordingly, such an interferometer can be made compact and light-weight, and the resistance to vibration is also improved.
Furthermore, it is desirable that the birefringent interferometer be equipped with a polarizer which polarizes the transmitted light or scattered and reflected light and directs this light onto the polarized light splitting birefringent element, an analyzer which polarizes the split light emitted from the polarized light splitting birefringent element, converging means which cause convergence of the light polarized by the analyzer and thus form an interferogram, and a photo-detector which detects this interferogram.
As a result, background components can be removed and the intensity of the interferogram can be doubled by taking the difference between an interferogram obtained with the directions of polarization of the polarizer and analyzer set parallel to each other and an interferogram obtained with the directions of polarization of the polarizer and analyzer set perpendicular to each other; accordingly, the S/N ratio can be increased even further.
Furthermore, if light adjustment means that narrow down or reduce the transmitted light or scattered and reflected light are installed between the measurement site holder and the birefringent interferometer, the light that is incident on the birefringent interferometer can be adjusted by being narrowed down or reduced; accordingly, the S/N ratio of the detected light can be increased even further.
Furthermore, the polarized light splitting birefringent element may be either a Savart plate or a Wollaston prism. As a result, the polarized light splitting birefringent element can easily be constructed, and a noninvasive optical bioinstrumentation device can be appropriately realized.
This measurement site holder is a measurement site holder for the exclusive use of each individual patient which is mounted on the side of the measuring device in order to acquire living-body information from the patient, and in which the measurement site of this patient is placed. This measurement site holder is wherein the holder is equipped with a recording medium which records living-body information acquired from the individual patient and/or measurement parameters used at the time of measurement, and is constructed so that the holder is detachable with respect to the measuring device side.
In the case of a measurement site holder constructed as described above, the measurement site of the patient is placed in a measurement site holder for the exclusive use of the individual patient which is mounted on the side of the measuring device, so that living-body information that is acquired for this patient is recorded on the recording medium of the measurement site holder that is currently mounted on the side of the measuring device.
Since this measurement site holder is made detachable with respect to the side of the measuring device, the measurement site holder can be carried/stored by the patient himself, and there is a one-to-one relationship between the measurement site holder for the individual patient that is thus carried/stored and used at the time of measurement, and the living-body information for this individual patient. Accordingly, the erroneous reading of living-body information for individual patients is prevented; furthermore, as a result of the use of a measurement site holder for the individual patient equipped with such a recording medium, the acquisition of living-body information for this patient on subsequent occasions, and the read-out of living-body information recorded for this patient, can be accomplished using a device other than the measuring device used to perform measurements.
Here, working curves for the individual patient and information regarding living-body components of the individual patient determined using such working curves may be cited as concrete examples of living-body information for the individual patient that is recorded on the recording medium. Various types of information may be cited as examples of such information regarding living-body components; blood sugar levels may be cited as a concrete example.
Furthermore, in concrete terms, a construction in which the measurement site in the measurement site holder is illuminated with light, the light that is transmitted through this measurement site or the light that is scattered and reflected by this measurement site is detected, and living-body information for the patient is acquired in a noninvasive manner on the basis of this detected light, may be cited as an example of the construction used to acquire living-body information for the patient.
Here, if a measurement site holder for the exclusive use of the individual patient is manufactured so that this holder conforms to the shape of the measurement site of the individual patient, the measurement site holder and measurement site show rough agreement; accordingly, the patient is much more effectively prevented from accidentally taking the wrong measurement site holder.
The abovementioned measurement site holder is a measurement site holder which is attached to a base that is disposed in the light path of the light that is incident on the photo-detection system. This measurement site holder is equipped with a main body part which has an opening into which the measurement site is inserted, and a base plate to which at least the tip end portion of the main body part is fastened, and which can be detachably mounted on a base. Furthermore, in cases where a portion of the measurement site protrudes from the measurement site holder, or in cases where there is no need to hold this protruding portion, it is desirable that an opening part be provided. It is desirable that the outside surface of this measurement site holder be coated with a coating in order to block external light, and that the inside of the measurement site holder be coated with a black coating material in order to prevent light that has passed through the tissues from escaping to the outside and re-entering the tissues, or that an optical filter be provided which is attached to the outside surface of the main body part.
An appropriate method for manufacturing the measurement site holder comprises the steps of forming a first resin mold which has an inside surface that matches the shape of the outside surface of the measurement site, forming a second resin mold which has an outside surface of the same shape as the outside surface of the abovementioned measurement site by introducing a resin into the first resin mold, transporting the abovementioned second resin mold to a specified factory, and forming a measurement site holder which has an inside surface that matches the shape of the outside surface of the abovementioned second resin mold at the abovementioned factory.